Exotic sphecid?

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Laverock
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Exotic sphecid?

I know this isn't the place for ID queries, but I would like the experts here to look at

http://www.ispotnature.org/node/436935

It looks to me like the continental mud-dauber Sceliphron destillatorium, but this does raise the awkward question of what it was doing in a car park in Chepstow. It's impressive, whatever it is. (I'm not the observer)

Nigel Jones
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Sceliphron

That is intriguing. My first thought was "that is going to be one of the parasitica", but the antennae look like Sphecid antenna, so this just might indeed be Sceliphron. Unfortunately the image is not clear enough to be definitive about which species this maybe (if indeed it is Sceliphron), as there are other species with the yellow petiole in Europe.

Let's see if we can get some additional opinions.

Nigel Jones
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George Else has kindly taken

George Else has kindly taken a look at the image and has considerable doubt about this being Sceliphron. George commented:

I’m not convinced the image is a Sceliphron species but some kind of ichneumonid. Although the photo is very poor, the abdomen  (metasoma) appears to possess a very short petiole, connecting it to the propodeum. In Sceliphron the petiole is always very long. I think one or more species in this sphecid genus have been inadvertently introduced into Britain in the past.

Laverock
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Side by side

In the image I have scaled the iSpot picture and placed it alongside a Sceliphron destillatorium from http://www.forum.hymis.de/viewtopic.php?f=14&t=5103 (I hope this is copyright-OK for Scientific Research, or Fair Comment, or something). I will leave you to compare the colouration of the legs, scutellum, tegulae and scapes; and the curl of the antennae; and direct your attention to the parallel green lines spanning the visible petiole on the right. If you look carefully at the left insect you can see the petiole picked out by light and shade between the ends of the lines, and it is exactly the same length. I cannot see any significant difference between the two, certainly not such as to suppose the Chepstow insect is "some kind of ichneumonid".

Nigel Jones
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That is quite convincing

That is a very useful comparison. One of the troubles with images, is that it is not always straight forward to discern the salient features, but looking at your very useful scaled comparison, that certainly looks like a Sceliphron petiole.

 

The species may have to remain uncertain though, as there is at least one other European species with the yellow petiole - S. spiriflex. It is also possible that the wasp may have been inadvertently imported from a place outside Europe, so it could be any one of a number of similar looking species? I'm not sure what the diagnostic features are for the various species, so without doing a deal of research it will be difficult to get any further than "probably Sceliphron".

 

A little frustrating. Identifying aculeates is usually a fraught business! None-the-less this is a very nice wasp to see in the UK!

Ian Cross
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Sceliphron prob ID

The more I look at the original image the more I am convinced that it is a female Sceliphron. The tegulae and postscutellum are marked with yellow which rules out spirifex. The distribution of yellow markings fits destillatorium best and I would be happy to say it is probably that species. However, in the absence of a specimen or more information on its origins we will never be able to say for sure.

Fascinating find all the same.

Ian Cross
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Sceliphron introduction via containers

Why Chepstow? It strikes me that Chepstow lies at the hub of transport links between several container ports: Newport, Avonmouth (and possibly Sharpness?) and the rest of the country. It's apparently quite common for Sceliphron to travel the globe in this fashion. A female has time to build a nest on a container (which provides a range of attractive corners and overhangs) while it sits for ages at some dock in a distant country. The emerging wasps then find themselves transported to the other side of the globe. Sceliphron caementarium is notorious for this though, from what I can make out, this does look more like destillatorium. I can't see enough detail to count antenna segments but, counting what I can and then extrapolating, it looks like 12. Ichneumons usually have more thread-like antennae with at least 13 and usually many more segments. This certainly looks like a female Sceliphron to me.

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